Driver design question

[Lee Revell <rlrevell@joe-job.com>]

I have a device here that can play PCM, but it's a weird implementation.
Only 2 periods of 0x2000 words per buffer are supported, and there is no
DMA - the driver must poll a status register, and when the chip is
ready, deliver all 0x2000 words using outw() then send an end xfer
command.

I think I need to use an intermediate buffer, and implement copy/silence
callbacks that write to this.  Then I plan to use a tasklet or workqueue
to do the actual xfer of PCM data to the hardware.  A timer callback
will periodically check whether at least 0x2000 words are in the buffer
and if so, schedule the tasklet to drain it.

I presume this implementation cannot support mmap() as there's no random
access to the hardware buffer.  Is this correct?

Do I call snd_pcm_period_elapsed() from the timer, immediately before
scheduling the tasklet, or from the tasklet, after the data has been
transferred to the hw?

In general, does this seem like a reasonable implementation?

Lee


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